Miklós Rózsa lifted liberally from his own work for this film when he later composed the score for El Cid (1961).
Stanley Baker was cast at very short notice after the actor first cast, George Sanders, had to be replaced due to illness. Baker was cast as Mordred due to his acclaimed portrayal of a villainous Royal Navy officer in The Cruel Sea (1953).
Anne Crawford, who plays Morgan Le Fay, was only 7 years and 3 months older than Stanley Baker, who plays her son Modred.
Powerscourt waterfall in Co. Wicklow Ireland was also used in two other Arthurian epics, "Excalibur" and "King Arthur".
The British release main title is slightly different from the US version. After the composer credit "Music by Miklós Rózsa," the British caption continues "London Symphony Orchestra conducted by Muir Mathieson." This is because whilst the main score was being conducted by Rozsa and Johnny Green in Hollywood, Mathieson also had to conduct it in London to satisfy demands of the English musicians' union. When Rozsa (who scored the same team's Ivanhoe (1952)) suddenly became available again, Clifton Parker was dropped and the LSO were out of a job, (only one Knights of the Round Table cue by Parker was retained). The Mathieson sessions were released on a Varese Sarabande album in 1980, although for legal reasons the performers were credited as the MGM Studio Orchestra and Chorus (UK). Some researchers in the Miklos Rozsa Society believe that the Mathieson sessions were used to score the simultaneously filmed Academy ratio version that went out to many British cinemas not yet equipped with CinemaScope. Possibly the Rozsa/Green recording (which was made available on a Film Score Monthly CD in 2003) may not have been sufficiently in sync to accommodate the two separate prints.